Slip casting and cold forming are well-known methods to form a desired shape from a powdered material.
In conventional slip-casting practice, the material to be cast is milled or otherwise processed into a finely divided powder of predetermined particle size generally between 1-5 microns. The finely divided material is then mixed with a liquid-suspending medium to form what is conventionally known as a slip which is poured into a suitable mold, e.g., a plaster of Paris mold. In the mold, the liquid suspending medium is drawn by capillary action into the body of the mold, and the remaining solids are deposited in coherent form. After drying, the shape may be removed from the mold and further processed into a final product.
For effective casting, a deflocculent should be included in the suspending medium to bind the different size particles into a uniform suspension so that the final product does not have a segregated structure. For non-oxide ceramic refractory materials such as borides, carbides, nitrides and silicides the liquid suspending medium requires an organic vehicle, i.e. the suspending medium cannot be an aqueous slurry. Presently, a small amount of a low molecular weight polymeric cyclopentadiene is used as the deflocculent of choice and is dissolved in an organic suspending medium selected from the group consisting of xylene, toluene, benzene, naphtha, and alcohol. The cyclopentadiene is generally added in a proportion of 5-12 percent by weight of the slip-suspending medium.